1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) and a method for driving the LCD. More specifically, the present invention relates to a vertical alignment (VA) mode LCD that may obtain a wide viewing angle without the formation of a cutout or a protrusion in the common electrode.
2. Discussion of the Background
Liquid crystal displays (LCDs) are one of the most widely used flat panel displays. An LCD includes a pair of panels provided with field-generating electrodes, such as pixel electrodes and a common electrode, and a liquid crystal (LC) layer interposed between the two panels. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer that determines the orientations of LC molecules therein to adjust polarization of incident light.
Among LCDs, a vertical alignment (VA) mode LCD, which aligns LC molecules such that the long axes of the LC molecules are perpendicular to the panels in the absence of an electric field, is spotlighted because of its high contrast ratio and wide reference viewing angle. A wide reference viewing angle is defined as a viewing angle that makes the contrast ratio equal to 1:10 or as a limit angle for the inversion in luminance between the grays.
The wide viewing angle of the VA mode LCD can be realized by cutouts in the field-generating electrodes and protrusions on the field-generating electrodes. Since the cutouts and the protrusions can determine the tilt directions of the LC molecules, the tilt directions can be distributed in several directions using the cutouts and the protrusions such that the reference viewing angle is widened.
However, in order to form the cutouts in the pixel electrode and the common electrode, an additional mask to pattern the common electrode is needed, and an overcoat to prevent the pigments of the color filter from contaminating the liquid crystal layer through the cutout of the common electrode should be included on the color filter. Furthermore, in order to form the protrusions, an additional process is needed or the existent process should be changed, and thus the manufacturing method of the liquid crystal display becomes complicated. In addition, the LC molecules disposed close to the protrusions or the cutouts are controlled in a VA mode LCD, but because the influence of the protrusions or the cutouts is weaker on the LC molecules disposed away from the protrusions or the cutouts, the response speed of the display device may decrease.